A novelty study conducted on the subject matter of this application, resulted in the citation of the following U.S. Pat. Nos.: 3,792,232; 3,794,809; 3,864,545; 3,895,218; and 3,995,142. Of the patents cited, the only one which appeared relevant to the subject matter presently claimed in this application is U.S. Pat. No. 3,995,142.
U.S. Pat. No. 3,995,142 issued on Nov. 30, 1976 for Defogging Rear Window Pane for Motor Vehicles. The structure defined in this patent is one wherein a plurality of spaced, wire heating elements are embedded in a pane of glass. A relatively short metallic collector, also embedded in the glass pane and having a circular segment configuration, is provided in each peripheral side of the pane at opposite margins thereof. A central wire heating element extends between the collectors in a rectilinear path. Additional wire heating elements above and below the central element have a rectilinear central portion parallel to the central element and are connected to the collectors by end portions converging on the respective collectors. The respective collectors have an appendix extending outwardly beyond the window weatherstripping to serve as a terminal for connection to a power source.
Also known at the time of the invention described in this specification, is an electrical heater plate 10 such as shown in FIG. 1 of the drawings. Such an electric heater plate 10 is used in vehicles manufactured by the Ford Motor Company which are equipped with electrically heated backlites. In particular, the electrical heater plate is formed from a base which is a tempered glass sheet 12. The tempered glass sheet has a plurality of thin lines 14--14 of a silver ceramic material bonded to one surface of the tempered glass sheet. The method by which such thin lines are formed on the glass sheet is by a silk screening operation which is well known in the art. The materials used in the process are also well known in the art, for example, see Column 2 of the aforementioned U.S. Pat. No. 3,895,218.
At the left hand and right hand sides of the thin lines 14--14, only the right hand side being shown in FIG. 1, there is an enlarged interconnection strip 16 having a width greater than one-half inch and formed of silver ceramic material interconnecting the associated right hand or left hand ends of the thin lines 14--14. The interconnection strip also has associated therewith an enlarged termination area 18. A copper strip 20 is soldered at locations identified by the numeral 22--22 to the interconnection strip 16, whereby electrical interconnection is made along the interconnection strip 16. An electrical lead 24 is soldered at position 26 to the termination area 18 of the interconnection strip 16, whereby electrical interconnection may be made between the electrical lead 24 and an electrical circuit, not shown, which provides power to the lines 14--14, which in turn provides heat to the tempered glass sheet 12 in order to de-ice or de-fog the same.
The structure proposed in this application is one which substantially reduces the amount of silver ceramic material used to form an electrical heater plate which can be used, for example, as a rear window in a motor vehicle. The reduction in the amount of silver ceramic used provides two benefits. A first benefit is that the cost of the structure is reduced because less silver is used in forming the structure. The second benefit achieved is that the interconnection strip of a wide dimension, as identified by the numeral 16 in FIG. 1, is substantially eliminated and replaced by interconnecting structure which can be more easily hidden by moldings over the rear window when the window is an installed position in a motor vehicle.